Menu
I recently attended an interview and they asked me the question "Why Interfaces are preferred over Abstract classes?"
I tried giving a few answers like:
They asked me take any of the JDBC api that you use. "Why are they Interfaces?".
Can I get a better answer for this?
437
The short answer: An abstract class allows you to create functionality that subclasses can implement or override. An interface only allows you to define functionality, not implement it. And whereas a class can extend only one abstract class, it can take advantage of multiple interfaces.
If you are creating functionality that will be useful across a wide range of objects, then you must use an interface. Abstract classes, at the end of the day, should be used for objects that are closely related. But the interfaces are best suited for providing common functionality to unrelated cases.
Type of variables: Abstract class can have final, non-final, static and non-static variables. The interface has only static and final variables. Implementation: Abstract class can provide the implementation of the interface. Interface can't provide the implementation of an abstract class.
A class can be instantiated i.e, objects of a class can be created. An Interface cannot be instantiated i.e, objects cannot be created. Classes does not support multiple inheritance. Interface supports multiple inheritance.
That interview question reflects a certain belief of the person asking the question. I believe that the person is wrong, and therefore you can go one of two directions.
The answer that they want, well, the other posters have highlighted those incredibly well. Multiple interface inheritance, the inheritance forces the class to make implementation choices, interfaces can be changed easier.
However, if you create a compelling (and correct) argument in your disagreement, then the interviewer might take note. First, highlight the positive things about interfaces, this is a MUST. Secondly, I would say that interfaces are better in many scenarios, but they also lead to code duplication which is a negative thing. If you have a wide array of subclasses which will be doing largely the same implementation, plus extra functionality, then you might want an abstract class. It allows you to have many similar objects with fine grained detail, whereas with only interfaces, you must have many distinct objects with almost duplicate code.
Interfaces have many uses, and there is a compelling reason to believe they are 'better'. However you should always be using the correct tool for the job, and that means that you can't write off abstract classes.
127
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
